Textiles include apparel items, home furnishings, carpets, and non-woven fabrics, such as disposable clothing and utility wipes, are generally two-dimensional, pliable and made from fibers or fibrous materials consisting of natural or man-made components. The manufacture of textiles includes fiber production and preparation as well as finishing processes which are applied to textiles near the completion of the manufacturing process.
Finishing steps may include addition of an anti-wrinkling agent; addition of a softening agent to improve the “hand ” of the fabric; addition of a flame-retardant chemical to reduce the flammability of the product; or addition of a fluorochemical or hydrocarbon-based treatment to reduce staining of the textile or to enhance resistance to penetration by liquids. A number of finishing processes may be applied at the same time; there may be greater than ten steps in some apparel finishing operations. The use of multiple finishes in textiles has increased in recent years to meet consumer demands for fabrics that do not wrinkle or stain, that have a smooth and comfortable feel, and that can be easily cleaned.
Some finishes are designed to counter the natural properties of fibers that are used in manufacture of the textile. For example, cotton is naturally absorbent and breathes well, making it cool and comfortable to wear; however, those traits also permit cotton fabric to be easily stained, absorb water, and dry slowly. As another example, polyester fabric tends to be hydrophobic, and therefore naturally stain repellent. However, polyester does not absorb perspiration well and therefore may feel “hot ” to some wearers. To overcome these drawbacks, textile manufacturers frequently add finishing chemicals that render cotton hydrophobic, and therefore less prone to absorb water or stains, or render polyester more hydrophilic, and therefore more comfortable to wear. The use of finishing processes is not limited to apparel: draperies may be prone to fading, and therefore can benefit from addition of a fade-resistant coating. However, that same coating may degrade the appearance of the product as seen from the inside, where fade-resistance is not needed. A non-woven wipe may be treated with a hydrophilic chemical to increase its ability to absorb spills, but it may be desirable to prevent the absorbed liquid from penetrating to the other side of the wipe.
It would be desirable to develop a treatment method, whereby two dimensional textiles can be exposed to finishing treatments that are different, or have different properties on each side. For example, an item of clothing might have a stain- and water-repellent coating on the outside, and be water-absorbent on the inside, such that it is stain-free, while remaining comfortable to wear. Similarly, a drapery that has a reflective or shiny, fade-resistant coating on the side facing the outside, might have a soft, satiny appearance on the side facing the inside of a room where fade-resistance is not needed.
The ability to clean, or remove stains from the product is enhanced by allowing the stain-release process to happen from the inside of the fabric. Difficulties in achieving dual-functionality treatments therefore result from the methods most commonly used for application of finishing treatment: the dip and cure process, or the dip and dry process. That is, most finishes are applied by pulling the fabric through a liquid chemical bath that contains a formulation for imparting the desired finish when the fabric is dried or cured, for example, in a subsequent heat step. Because there is no easy or inexpensive way to keep the liquid chemicals on only one side of the fabric, the entire material, including both sides, is treated at once.
Previous methods for achieving side-specific functionality include those described in U.S. Pat. Nos. 5,065,600, 5,312,667 and 6,151,928, where hydrophilic and hydrophobic yarns are knitted into a composite textile having opposing absorbent and non-absorbent faces. These methods are specific to knitted fabric and require very specific knit patterns. A composite textile in which hydrophobic and hydrophilic fabrics are sewn together resulting in an outer zone providing a leak-proofing function and a hydrophilic inner zone allowing mass and heat to be transferred to an intermediate zone between the two fabrics is described in U.S. Pat. No. 6,955,999. This method is applicable to more general types of fabrics, but is likely to result in reduced comfort.
A plasma-based method to achieve side-specific finishing is described in U.S. Pat. No. 6,187,391; however, the method requires the application of a sizing agent to one side of the fabric to mask the effect of plasma treatment on that side. The masking step is followed by plasma treatment and subsequent graft-polymerization of a coating onto the unmasked, plasma-treated sided. Finally, the sizing must be removed to regain the original functionality on the masked side. Single-sided application of sizing is a complex process, presenting the same difficulties which would be encountered if one applied a functional finish selectively to one side of the fabric. Moreover, graft polymerization, where radical-initiated polymerization is induced by residual radicals left on the fabric surface after plasma treatment, is a relatively slow process which takes tens of minutes or even hours of exposure to gas-phase monomers.
Accordingly, it is an object of the present invention to provide a method and apparatus for selectively processing one side of a treated fabric in such a manner that the other side of the fabric remains essentially unaffected.
Another object of the invention is to provide a method and apparatus for selectively removing a coating from one side of a coated fabric, such that the coating on the other side of the fabric remains essentially unaffected.
Still another object of the present invention is to provide a method and apparatus for selectively attaching chemical functional groups to the surface of a coated fabric or coated nonwoven material on only one side, such that the chemical functional groups impart a different property to that side than was originally present thereon.
Yet another object of the invention is to provide a method and apparatus for selectively removing a portion of or all of a hydrophobic coating from one side of a coated textile, such that the textile may be treated with a second coating which will only adhere to the non-hydrophobic side.
Additional objects, advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.